In a market of displays, high-resolution displays are more and more popular for their fine display quality. A higher resolution display with a fixed display size requires metal lines therein to be thinner.
The metal lines are generally formed by a patterning process typically including: coating photoresist at a thin film; exposing the photoresist with a mask; washing out a portion of the photoresist to be removed with a developer solution; etching off a portion of the thin film which is not coated with the photoresist; and finally peeling off the remaining photoresist. Currently, the portion of the thin film which is not coated with the photoresist is usually etched off by a wet-etching process.
However, in practical production, as shown in FIG. 1, it is difficult to prevent dust 1 in an environment from entering an interface between the photoresist 2 and the metal film 3; or, as shown in FIG. 2, it is very likely that crack exists in a side of the photoresist 2. Then, during the wet-etching process, it is very likely that etching liquid flows into a region below the photoresist due to the presence of the dust or the crack, as a result, a portion of the metal film below the photoresist may be etched off.
Meanwhile, during the wet-etching process, the phenomenon of drill etching may appear due to the fact that capabilities in all directions are same for the wet etching process, i.e. etching is implemented in all directions at a same rate. When the etching liquid flows into the region below the photoresist due to the presence of the dust or the crack, the drill etching may intensify the etching of the portion of the metal film below the photoresist and enlarge an etching range.
As a matter of fact, the portion of the metal film below the photoresist should be remained. When the metal lines are etched by the wet-etching process, sizes of portions of the metal line may be smaller than a desired size of the metal line. As the desired size of the metal line is small, the portions of the metal line may be too thin or even be broken, therefore, the display device is degraded and even cannot work properly.